Research seems to show that Hackers are more likely to make small-scale attacks on networks on a regular basis, as opposed to singular, large and devastating attacks.

"Study of the Zotob worm demonstrated that, compared to earlier worm outbreaks such as SQL Slammer or Sasser, Zotob adversely impacted significantly fewer organizations," said Russ Cooper, Cybertrust senior information security analyst and author of the Zotob study.

"The nature of this worm and its ultimate business impact illustrates the goal of hackers today is no longer widespread system shutdown, but rather more frequent, smaller attacks with specific targets powered by a drive for financial and information gain," he added.
It is important to note that many victims of the Zotob worm were hit because no firewall had been installed.